This disclosure is directed toward a series of vanadium phosphate glasses that are an effective flame retardant, and more specifically, when compounded with a polyolefin, the glasses retard combustion and can reduce combustion to the point of self extinguishing of the polyolefin. The compound is useful for fabricating fire retardant plenum cables.
The recent trend toward the use of “green” materials has prompted more research in the flame retardant industry for non-halogenated materials for use in plenum cables. Halogenated flame retardants, while extremely effective, can decompose during processing and corrode processing equipment. Halogenated flame retardants may also produce gaseous hydrogen chloride, hydrogen bromide, or hydrogen fluoride during combustion, which are harmful to the environment. At present, Polyvinyl Chloride (PVC) or Teflon® based materials will pass the rigorous testing used to qualify a cable for plenum applications in the fiber optic cable industry, but at a relatively high cost.
So-called “commodity” polymers, such as polyolefins are low cost material alternatives for plenum cable jackets. Unfortunately, the polyolefin family of polymers burns very well, so developing flame retardants for commodity polymers that will pass the rigorous testing required for cable applications is exceedingly difficult. Currently, most flame retardant polyethylenes contain high levels of magnesium dihydroxide (MDH) or aluminum trihydrate (ATH). While effective for some less demanding applications, these materials will not pass testing for plenum cable jackets. In addition, ATH starts to decompose at 190° C., which limits its use to polymers with low processing temperatures.